VPS vs. VDS: The Second Virtualization Decision

In today's business world, server virtualization commands ever-increasing market share, and there's little wonder. Providing both cost savings and relative simplicity, a VPS hosting is a logical choice when customer requirements move beyond simple web page hosting.

But the decision to contract for a virtual server requires an important additional choice. Virtualization vendors offer two types of service: virtual private servers (VPS) and virtual dedicated servers (VDS). While both services offer the advantages of virtualization, there are significant differences between them. These differences need to be compared with customer needs in order to make the best, most effective choice.

Virtual Private Server (VPS)

A VPS is, in architectural terms, container-based. This means that the hosting hardware is loaded with a major operating system, such as Linux. Virtualization software, such as the Virtuozzo VPS, runs under the Linux operating system. Each VPS runs in a "container" managed by the virtualization software.

The operating system sees the virtualization software as a single large task, and each "containerized" VPS becomes a sub-task.

This arrangement provides major benefits to both the server vendor and the customer. Management can be very efficient, as there is only a single copy of the major operating system running directly at the hardware level. Each container can share operating system code, avoiding duplication in both installation and maintenance. Sharing of resources in this manner lowers operational costs and yields more performance per hardware dollar.

Of course, there are some disadvantages. Use of a shared operating system means that customization of an individual VPS will generally not be possible. As well, the number of VPSs that can be hosted on a single hardware platform is somewhat limited, and in turn, scalability is limited. Finally, system administrator or "root" access is not usually available to the VPS customer.

Virtual Dedicated Server (VDS)

The architecture of VDS hosting differs substantially from VPS hosting. VDS technology uses a "hypervisor" product, such as the Hyper-V VDS , to manage virtualization. The hypervisor software runs directly under the hardware layer rather than under another operating system. The hypervisor directly controls a number of subsidiary virtual machines, each of which is effectively independent. Each virtual machine has its own set of resources.

The consequences of this arrangement are significant. Since each virtual machine is independent, the server customer has full control and full "root" access at the virtual machine level. There is no shared code, and the only shared resource is the hypervisor itself. VDS platforms tend to be larger than VPS platforms, allowing the vendor to host more virtual machines and the customer to have enhanced scalability.

One disadvantage, however, is generally higher cost. The customer also becomes responsible for all operating system installation and maintenance.

Making the Choice

Customers should ask themselves the following questions to guide their decision when choosing between a VPS and a VDS.

1. Is cost an object?

Minimal cost will be achieved with a VPS, and this is the logical choice when the advantages of virtualization are desired on a more limited budget. This

also may be the right option for the customer who simply wants to try out virtualization or who has modest resource and performance requirements.

For business-critical applications, where cost is secondary, the decision will likely be based on non-cost factors.

2. Is significant growth anticipated?

A hypervisor-based VDS offers the best growth path. For customers who anticipate rapid business growth and changing resource needs, a VDS is a clear choice. On the other hand, modest growth scenarios and relatively static resource needs may make a container-based VPS the right option.

3. How important is flexibility?

For customers with little need or interest in operating system customization, and who are able to work with a standard Windows or Linux installation, a VPS is a likely choice. If customization is required, a VDS needs to be selected. "Root" access will also require the choice of a VDS. Since the use of some software requires "root" access, customers need to consider this point with special care and attention.

4. Who will do operating system maintenance?

This is a very important question. Many customers are not prepared or simply don't want to do the operating system maintence required by a VDS. For them, a VPS may be the necessary selection. Customers with technical staff capable of installation and maintenance work can confidently choose a VDS when business needs support such a decision. An additional option is to contract for operating system support, eliminating the need for dedicated technical staff.

Conclusion

Leading products such as Virtuozzo VPS and Hyper-V VDS make virtualization technology nearly transparent, giving customers the full effect of server hosting without the need to buy and maintain expensive hardware platforms. Choosing between commercial VPS or VDS hosting options requires some analysis of current and future needs, and outstanding results will be obtained with a little time and care.